Morphogens 1 Flashcards
What gene was identified as being abundant in the head region of Xenopus embryo?
Cerberus (three headed dog!).
What does injection of cerberus into vegetal blastomeres cause?
Ectopic head structures but no secondary axis.
What is the primary function of cerberus in the developing embryo?
To inhibit nodal, BMP, and Wnt signalling. This allows head formation.
What happens during Xenopus development if we knock down cerberus? What about if we also knock down Dickkopf and Frzb?
Nothing, because of redundancy. Triple-knockdown results in a loss of head structures.
How is β-catenin involved in Wnt signalling?
When Wnt is active, β-catenin is free to migrate to the nucleus where it acts as a transcription factor.
What is the general role of Wnt signalling when specifying the Xenopus body plan?
To act as a trunk inducer.
What gene along the anterior-posterior axis at the neural plate stage is later expressed in the forebrain?
Krox20.
What gene along the anterior-posterior axis at the neural plate stage is later expressed in the forebrain and midbrain?
Otx2.
What gene along the anterior-posterior axis at the neural plate stage is later expressed in the hindbrain?
Bf1.
How did researchers show that Wnt was functioning in a concentration-dependent manner in the embryo?
They dissociated tissues and then exposed them to varying concentrations of Wnt, observing different tissue fates.
What morphogen gradient patterns the Xenopus anterior-posterior axis?
Wnt gradient.
What are the 2 criteria which must be satisfied for something to be acting as a morphogen?
- Forms a gradient of concentration
2. Different concentrations induce varied responses
What model tries to explain the idea that varying concentrations of a morphogen have sharp cutoff values in terms of tissue fate specification?
The French flag model.
What 2 adjacent tissues influence fate of cells in the neural tube?
- Ectoderm
2. Notochord
What differentiates the eventual function of the dorsal neural tube from the ventral neural tube?
Dorsal: receives signals from the PNS receptors (pain, touch, etc.)
Ventral: innervates the motor neurons